This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A new approach to controlling malaria-causing Plasmodium falciparum aims at the parasite's ubiquitin-proteasome pathway which is essential for its survival. Since the host's defense mechanisms against pathogens rely on the ubiquitin-proteasome system in antigen presentation and in the regulation of membrane trafficking, many viruses and bacteria encode proteins that act on the ubiquitin-proteasome pathway, yet there is a near-complete lack of data on this pathway in parasites. It was shown that the mammalian UchL3 ortholog in Plasmodium falciparum (PfUchL3) possesses deubiquitinating as well as deNeddylating activity. We are interested in determining the molecular architecture of PfUchL3 and revealing the mechanisms for the dual specificity towards ubiquitin and NEDD8. To this end we prepared crystals of the complex between PfUchL3 and the ubiquitin based suicide substrate UbVME.